Jet evolution in a dense medium : event-by-event fluctuations and multi-particle correlations
Escobedo Espinosa, M., & Iancu, E. (2017). Jet evolution in a dense medium : event-by-event fluctuations and multi-particle correlations. Nuclear Physics A, 967, 449-452. doi:10.1016/j.nuclphysa.2017.05.031
Published inNuclear Physics A
© 2017 the Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license.
We study the gluon distribution produced via successive medium-induced branchings by an energetic jet propagating through a weakly-coupled quark-gluon plasma. We show that under suitable approximations, the jet evolution is a Markovian stochastic process, which is exactly solvable. For this process, we construct exact analytic solutions for all the n-point correlation functions describing the gluon distribution in the space of energy [1, 2]. Using these results, we study the event-by-event distribution of the energy lost by the jet at large angles and of the multiplicities of the soft particles which carry this energy. We find that the event-by-event fluctuations are huge: the standard deviation in the energy loss is parametrically as large as its mean value . This has important consequences for the phenomenology of di-jet asymmetry in Pb+Pb collisions at the LHC: it implies that the fluctuations in the branching process can contribute to the measured asymmetry on an equal footing with the geometry of the di-jet event (i.e. as the difference between the in-medium path lengths of the two jets). We compute the higher moments of the multiplicity distribution and identify a remarkable regularity known as Koba-Nielsen-Olesen (KNO) scaling . These predictions could be tested via eventby-event measurements of the di-jet asymmetry. ...